Method of producing silicon-iron sheet material with boron addition and product

ABSTRACT

High-permeability silicon-iron sheet is produced by providing a melt containing about 10 parts per million boron, 45 parts per million nitrogen and about 0.030 per cent of manganese and sulfur, hot rolling from about 2250*F, and finishing with a final cold reduction of 80 per cent.

United States Patent 1191 Fiedler Sept. 16, 1975 METHOD OF PRODUCINGSILICON-IRON [56] References Cited SHEET MATERIAL WITH BORON UNITEDSTATES PATENTS ADDITION AND PRODUCT 3.575.739 4/1971 Fiedler 148/1 1 1[75] Inventor: Howard C. Fiedler, Schenectady, 7 5 10/1972 Tanaka et 4I43/ I l 3,725,143 4/1973 Alworth etal. 75 123 B [73] Assignee: GeneralElectric Company, FOREIGN PATENTS 0R APPLICATIONS Schenectady, N.Y.-7663 4/1965 Japan 148 11 1 22 F] d: S t. 16, 1974 1 le ep PrimaryExaminer-Walter R. Satterfield [2 l Appl. No.: 506,546 Attorney, Agent,or Firm-Charles T. Watts; Joseph T.

Related US. Application Data Cohen; Jerome Squmaro [6U]Continuation-impart of Ser, No. 429,791, Jan. 2,

I974, abandoned, which is a continuation-in-part of [57] ABSTRACT SBr.N0. Z n- I973, flbandflned- High-permeability silicon-iron sheet isproduced by providing a melt containing about 10 parts per million148/111; 75/123 B; 75/123 L; boron, parts per million nitrogen and about0.030 148/3155; 148/] per cent of manganese and sulfur, hot rolling from[S 1] Int. Cl. H0" 1/04 about 225mg and fi i hi with a fma| m reduction1581 Field of Search 148/111, 110, 112, 31.55; f 80 percent,

/123 B, I23 L l3 Claims, N0 Drawings I METHOD OF PRODUCING SILICON-IRONSHEET MATERIAL WITH BORON ADDITION AND PRODUCT This is acontinuation-in-part of my copcnding patent application Ser. No. 429.7%,now abandoned. filed Jan. 2. I974. which is a continuation-in-part of mypatent application Ser. No. 320.669. filed Jan. 2. W73 (now abandoned).both assigned to the assignee hereof.

The present invention relates generally to the art of makingpolycrystalline. magnetically soft. rolled silicon-iron products. and ismore particularly concerned with a novel method of producinghighpcrmeability. singly oriented siliconiron sheet including asessential features the use of boron in small but critical amount.nitrogen in the metal in critical ratio to the boron. the presence ofmanganese and sulfur in a ratio less than 2.1. a cold rolling scheduleincluding an intermediate annealing step and a final heavy cold rollingreduction. This invention additionally concerns a new hot-rolledsilicon-iron band product.

CROSS REFERENCES This invention is related to the invention disclosedand claimed in patent application Ser. No. 43l.l28 now abandoned. filedJan. 7. I974 as a COI'IIIIIUZIIIOI'PIII- part of patent application Ser.No. 326.852 (now abandoned). filed .Ian. 27. 1973. entitled Method ofProducing Oriented Silicon-lron Sheet Material With Boron Addition inthe name of Herbert E. Grenoble and assigned to the assignee hereof.which pertain to the concept of using small but critical amounts ofboron to enable the production of singly-oriented silicon-iron sheet.

The invention disclosed and claimed herein also relatcs to thatdisclosed and claimed in patent application Ser. No. 429.800. nowabandoned. filed .Ian. 2. I974. as a ctmtinuation-in-part of patentapplication Ser. No. 32ll.hb8 (now abandoned). filed Jan. 2. I973.entitled Method of Producing Oriented Silicon-Iron Sheet Material WithBoron Addition" in my name and assigned to the assigncc hereof. whichpertain to the novel concept ofcold rolling hot-rolled silicon-ironsheet directly to final thickness without an intermediate heat treatmentthrough the use of small but critical amounts of boron and bymaintaining the ratio of manganese to sulfur in the metal at less than[.5.

BACKGROUND OF THE INVENTION The sheet materials to which the inventionis directed are usually referred to in the art as electric-til siliconsteels or. more properly. silicon-irons and are ordinarily composedprincipally ofiron alloyed with about 2.2 to 4.5 per cent silicon andrelatively minor amounts of various impurities and very small amounts ofcarbon. These products are of the cube-on-edgc" type. more than about 70percent of their crystal structure being oriented in the 1 HUIHUItexture. as described in Miller Indices terms.

Such grain-oriented silicon-iron sheet products are currently madecommercially by the sequence of hot rolling. heat treating. coldrolling. heat treating. again cold rolling and then final heat treatingto dccarhurizc. dcsulfurize and recrystallize. lngots are conventionallyhot-worked into a strip or sheet-like configuration less than H.150 inchin thickness. referred to as hot rolled band." The hot rolled band isthen cold rolled with appropriate intermediate annealing treatment tothe finished sheet or strip thickness usually involving at least a 50per cent reduction in thickness. and given a final or texture-producingannealing treatment.

From time to time. there have been reports in the literature of methodsby which unusually high permeability silicon-iron sheet materials can beconsistently produced through departures from conventional practice inrespect to melt chemistry. rolling schedules and heat-treatingconditions. To the best of my knowledge. however. none of these methodshas proven to be entirely satisfactory. In some cases the cost is toohigh, while in others residues of processing additives defy removalefforts and penalize product magnetic properties.

SUMMARY OF THE INVENTION I have discovered that unusually highpermeability silicon-iron sheet material can be consistently produced bya novel process. the economics of which compare favorably with those ofpresent commercial operations. Thus. I have found that these results canbe obtained by making new departures from the present general practicewhich do not require modification ofconventional silicon-iron millproduction or processing equipment and do not significantly increaseeither labor or material costs.

In the practice of this invention. a silicon-iron melt containing atleast (H)! per cent manganese and being otherwise of ordinary chemistrycan be used. a small but critical amount of boron being added toestablish a nitrogen to boron ratio in the metal in the range of one tofifteen parts of nitrogen per part of boron and the ratio of manganeseto sulfur being adjusted to less than 2.l. Further. I have found thatfinished products of substantially improved magnetic properties can beobtained by cold rolling to an intermediate thickness and then heattreating the cold-worked sheet. and thereafter subjecting thesilicon-iron sheet to a final heavy cold reduction.

l contemplate in addition the use ofselenium in place of part of or allthe sulfur required in accordance with this invention. As in the case ofsulfur. the selenium requirement of this new process can be met invarious Ways. my preference being to add the requisite amount to theladle in elemental form or as ferroselcnium.

DETAILED DESCRIPTION OF THE INVENTION Generally described. my presentinvention comprises the steps of providing a silicon-iron meltcontaining 2.2 to 4.5 per cent silicon. manganese and sulfur in amountsin a ratio of manganese to sulfur of less than 2. 1. between about threeand 35 parts per million boron and between 30 and 60 parts per millionnitrogen in the ratio to boron of l to l 5 parts per part of boron.casting the melt to form an ingot. hot rolling the ingot. then coldrolling the resulting hot-rolled band to intermediate thickness. heattreating the cold-worked sheet. and then subjecting the silicon-ironsheet to a final heavy cold reduction. Thereafter. the cold-rolled sheetis subjected to a final heat treatment to decarburizc it and to developcube-on-edge secondary recrystallization texture in it.

Preferably. the boron content of the metal at the outset of the finalheat treatment is from 5 to 25 parts per million. such amount of boronin suitable form being added at the melt stage. It is contemplated.however. that the boron will be in amount from about three to about 35parts per million as l have found that addition of less than three ppmof boron to silicon-iron melts is not sufficient to consistently producethe new results of this invention. and amounts of boron greater than 35ppm require the presence of nitrogen in amounts in ex' cess of thosenormally obtained in conventional melting practice.

The boron content of the metal at the melt stage can differsignificantly from that at the hot-rolled band stage. particularly whenthe melt addition of the boron source is made early or when the ingot issoaked at unusually high temperature or for a prolonged period of time.Boron loss. however. has been found to be negligible when the boronsource is added to the ladle and hot rolling is begun as the ingotreaches hot rolling te mperature as subsequently described. Thus. it ispossible in carrying out this invention process to produce a hotrolledband and a cold-rolled sheet of final gauge thickness which haveapparently the same bulk contents of boron. nitrogen. manganese andsulfur as the melt in the ladle from which they were derived. By thesame token. it is possible to produce such band and sheet materials ofsubstantially different chemistry. The important consideration. however.is the composition of the band or sheet. particularly in terms of theforegoing four elements and their critical ratios during the coldrolling and intermediate and final annealing stages of this process.

lt will be understood from the foregoing that this invention has botharticle and method aspects. the new product being a hot-rolled bandcontaining 2.2 to 4.5 per cent silicon. manganese and sulfur in theratio of manganese to sulfur less than 2. l between about 3 and 35 partsper million boron. and between 30 and 60 parts per million nitrogen inthe ratio to boron of l to 15 parts per part of boron.

The boron content of ordinary silicon-iron is negligible. proving on wetanalysis to be less than one part per million. Accordingly. forpractical purposes in this specification and the appended claims. theterms boron content" and boron addition in their various forms have thesame essential meaning.

Permeabilities in the rolling direction of typical prod ucts of thepresent invention l l-mil strip materials) are of the order of [850 toI920 gauss as measured in a l-oerstcd magnetic field. The watt losses ofthese materials likewise are in a highly favorable range. being of theorder of 0.52 to 0.60 watt per pound (wpp) at l5.000 gauss and 0.67 to0.77 wpp at 17.000 gauss (60 hertz According to the present invention asI prefer to practice it. silicon steels containing about 0.03 per centof each manganese and sulfur. and about 0.03 per cent of carbon. andusual amounts of incidental impurities are produced in the form ofstrips or sheets for use in electrical equipment including transformersand mo tors by providing a melt of the required chemistry and adding toit a source of boron equivalent to to parts per million of boron toestablish a nitrogen to boron ratio of one to fifteen parts per part ofboron. Ingots cast from the melt are heated preferably to about 2200 to2300F and hot rolled in a series of passes until the thickness of theresulting sheets is about l00 mils. After pickling and annealing. thesheets are cold rolled to intermediate thickness of about 60 mils andreheated and then cold rolled again to final thickness of about l mils.Thereafter. the cold-worked sheet is given a dccarburizing heattreatment and a recrystallizing (texturizingj anneal during which boronis largely. if not entirely. eliminated from the sheet or strip product.

ln a commercial-scale operation designed to test the capabilities ofthis new process in a production'type operation. a -ton melt wasprepared using BOF silicon-iron. Five parts per million of boron in theform of i'erroboron were added to the melt in the ladle. which then hadthe following composition:

Silicon 1 l5 percent (oppcr 0 24 hromium 0.033 Aluminum 0.005 Manganese0.035 Sulfur 0.03l Carbon 0.030 Boron 0.0006 Nilruge'll 0.01150 lronRemainder Eight ingots were cast from this melt and four of these wereheated to 2350 for hot rolling, while the other four were heated to2250". Hot rolling was carried out in accordance with standardproduction prac tice in a six-strand tandem hot strip mill to providehotrolled bands from to l 30 mils thick. Samples of the hot-rolled handfrom the butt and hot top end of each hot-rolled coil were pickled inthe conventional acid solution and then heat treated in hydrogen forapproximately 3 minutes at 900C. Some of these sample ieces were coldrolled without tension directly to a thickness of approximately l lmils. while others were cold rolled without tension to 60 mils thicknessand then heat treated in hydrogen for 3 minutes at 900C before rollingto l l mils.

Epstein-size strips of all the resulting coldrolled sheet materials weredecarburized at 800C in hydrogen (room temperature dewpoint) by heatingfor 3 min utes. The strips comprising the Epstein pack were lightlydusted with alumina powder and stacked and then heat treated. beingloaded at 800C and heated at 50C per hour to 10S0C in nitrogen and thento ll50"C in hydrogen where they were held for two hours. Magneticproperties of the Epstein packs are set forth in Tables I and ll.

As shown by the data in Tables I and II. both ends of a coil moreconsistently develop high permeabilities and low losses if a heattreatment step at 60 mils is included in the cold-rolling schedule.Furthermore. it is apparent from these data that very good magneticproperties are more consistently obtained in these materials when hotrolling is begun at 2250F than when the temperature of the ingot at theoutset of hot rolling is [00F higher.

TABLE l Magnetic Properties ol Stun Hol Rol|ed From 2350? TABLEl-Continued Magnetic Properties ol Strip Hot-Rolled From 2350 F Themanganese and sulfur analyses and the boron added in each instance areset out in Table I]! together with the rolling and heat-treatingconditions and the re- (iage Losses. Inwpp salts of permeability andwatt loss measurements made (ml Location MIls ISUkB lhjkli I'HlkB alllH5 on each individual finished prfiduct Two Staged Rolled (6U MilIntermediate (iagc) I Butt H2 524 Mu n77 luo} A I Hot H 3 Ml ma) HamSlices l.75 Inch thIck were cut trom SU-pound ingots j r cast from eachmelt of this series and heated either to ot o I. y s. 5 Bun p H2 5W M7(7U I 175C or l2(l(l( for hot roll ng. as noted In Table Ill. 5 Hot lopIL: 53! 62*) as! Isun The ingot portions were hot rolled to 90 milsthickness in six passes without reheating. Each resulting hot- TABl Erolled band was pickled and then cold rolled to intermediate thicknesseither of 60 mils or of 28 mils. then heat treated for three minutes at900 in h 'dro en d Magnetic Properties of Strip HobRolled Front IISUI" qg age [40mgv mwpp finally cold rolled to l lm1l thickness. (Nominal ll-nnl (oil Location Mils Isokn 16,3I-4B 17am NIH strip ranged in theseruns from 11.0 to ll.3 mils in Direct Cold Rolled thlckncss' 1 Butt Ill(33 7uo was Ins :3 I a Epstein strips of each of these cold-rolled sheetProdi L i 7 Hot lop II. 1 5% 7m 7:44 lsftn ucts were decarburized by subecting them for 3 mm- 8 Butt utes to a temperature of 800C in hydrogenat room s Hot l'op H1 594 7I2 79o II 27 3 M )d Th f h l l'uo StagedRolled [o Mil intermediate (iagc) L'WljolnL or t 8 1nd dnned Wat (I Bunll 2 l NIX I loss strips (3 cm X 30.5 cm) were lightly dusted wIth 6 Hotlop ll 1 54) 644 703 lXUU t 7 mm U 538 62 77 W25 alumina powder andstacked. Patks of l 1 mil strlops 7 Hot lop I I} 55a 05a 7w Imn wereloaded at 800C. heated at 50 per hour to 1050 C H i f in nitrogen andthen to l l5UC in hydrogen, where they it Hot lop ll I 3! (13h (U3 lX lIwere held for 2 hours.

TABLE III Magnctic Properties of l-pstcin Packs of l l Mil Thick StripsProcessed With An Intermediate Hcat lrcatment Heat 'lrcatcd at h!) MilsHeat 'l'reated at 28 Mils ppm B l osscsi mupp. til) Hert/ Losscs mwpp(it! Hert/ Run \tltl'.ti I Mn "l s Mn/S Isak-Ii Inna; ,ultlH IS an;I7.nkn Ian I 5 ma .Ull 2.7 Ion: I475 Hlltl 15824 3 l5 am now 3,3 777lntl4 n45 s 17m 1 o n34 vIII7 2n s78 i i543 n3l 9H2 I72! 4 5 .Im .Ulh2.I n27 l727 Shl 7113 1x3? 5 on on 2,0 524 704 I 7n 537 7:4 Ix-u (I nH33 .035 I 1 10m I444 on x4 i779 7 5 H36 n 1.4 54x 70v Iss3 54s 74! Is4ss In n34 n21 Is 543 7I7 Iss6 555 740 I855 a 2o (:34 .Im 1.5 SR7 (ms wasSSI 723 Ixnn In 3o on .023 l 54s 7a: was 5x5 776 Iss0 ll an o2: L4 n33Ht) III S75 83H I756 I2 [I In: .033 In I054 I47s SQI s4I I772 I). 5 at:am an 555 m7 IvIm 500 725 I86!" 14 In M3} on In 555 7II min 575 7m 1x33I5 In an am as 567 73a liq-to This invention has been further exploredin a series of l5 experiments designed to test the composition andprocessing parameters, particularly the boron content. the manganese andsulfur content and ratio and the extent of thickness reduction duringthe final or second cold rolling phase of a two-stage cold-rollingprocess. In carrying out these experiments each of the heats was meltedin an air induction furnace in an argon atmosphere using electrolyticiron ot98 per cent i'crrosilicon to provide a melt of the followingcomposition:

Silicon i l percent (.Irhnn II oj upper (I l ('hronlnnn (Ltl Nllrngcn(Ill-i5 Iron Remainder Preparation of these and subsequent heatsresulted in nitrogen contents from 30 to 60 parts per million withabove-indicated average content.

As indicated by the data reported in Table Ill, the magnetic propertiesof the products were substantially improved by the addition of boronwhen the ratio of manganese to sulfur in the silicon-iron was less than2.1. Further. high permeabilities were obtained through the addition offive to 30 parts per million of boron, but the addition of 40 parts permillion of boron resulted in incomplete secondary recrystallization andconsequent substantially diminished permeability. Fi nally permeabilitywas improved by heavier final cold reductions. which is surprising inview of general experiencc in conventional practice to the contrary.

Four additional experiments were run as a series to test the two-stagecold reduction process against the single stage or direct cold reductionmethod. Permca bility and watt loss measurements made on finished l lmil silicon-iron strip materials resulted in the data set out in TableIV. which also indicates in each instance the rolling procedure andlists the amounts of boron added and the manganese and sulfur content ofeach individual melt of this series.

TABLE I\" TABLE VI nntpp (iugc lSkB lhulkli l7kll p10" A ll )lll I5]: I!H! H Slll 594 040 lull ltL J F5: -H (\Hi lUUZ t) 10.) in? has 734 1x7;

Comparison of Properties Obtained By Direct (old Rolling to l l MilsWith Heat l rcatment at Intermediate (iagc of (i0 Mils Rolling ppm B RunProcedure Added '1 Mn S lillkli l 0H1 ultlll In" Direct 5 0m: 00% ins75s 1x49 I7 00 mil [(5 55 ol7 lJlh IX Direct l0 00-11 0.03: 574 745 lNSSl 0 mil K; 530 MR 1908 Hill rolled liom ll'i'it' others hot rolled fromlllltl t proves the magnetic properties of the final product. ascontrasted to cold rolling direct to final gauge from the hot rolledbandv In addition. in view of the foregoing experimental results. itwill be understood that the final cold reduction carried out in thetwo-stage cold-rolling operation of this invention is preferably of theorder of at least (10 per cent and most desirably upwards of 70 or 80per cent. Acceptable or satisfactory results may. however. m

be obtained at reductions of the order of 50 per cent and even less.other factors influencing the develop ment of secondaryrecrystallization texture and good magnetic properties being the sameand within the crit ical limits defined above.

In laboratory experiments illustrating the utility of selenium in thisprocess. four heats were melted in an air induction furnace under anargon cover using electrolytic iron and 98 per cent ferrosilicon. Fiveparts per million of boron were added to each heat and (1.025 per centof selenium was added to two heats [B and C) and 0.045 per cent seleniumwas added to another (heat D). 'l he chemical analyses of these heatswere as follows:

in one instance in the course of carrying out this experiment. 0.020 percent of selenium was added to the melt which had the following analyzedcomposition:

' \ln '1 S (J03! (LOU-l tl,l)l5 1.] ill 0.0} .03

As in the other heats of this series. five parts per million of boronwere added to the molten metal and processing for one sample (X) was asdescribed above, while in the case of a second sample (Y). the intermediate heat treatment was carried out at l000(. instead of 900C. Themeasured magnetic characteristics of these final products were:

It is apparent that selenium is more effective than sulfur when comparedon an atomic weight basis at lcast Slices 1.75 inches thick from theresulting SU-pound ingots were heated to 1200C and rolled withoutreheating in six passes to a thickness of 90 to Hit) mils. Afterpickling, samples of the hot rolled band were heated in hydrogen for 3minutes, cold rolled to 60 mils. heated again for 3 minutes at 900C inhydrogen and cold rolled to the final thickness of l l mils. Epsteinstrips were decarburized by heating for 3 minutes at 800C in wethydrogen. after which they were separated with alumina powdcr and giventhe final anneal. The final anneal consisted of heating at C per hourfrom 800C to 10S0C in nitrogen. then in hydrogen to l l75( and holding 3hours. The magnetic properties of Epstein packs of these materials weremeasured with the following results:

.026 atomic per cent sulfur being required with 0030 per cent manganesebut only 0.0[7 atomic per cent of selenium being necessary.

As used herein and in the appended claims. the term ingot'- means andrefers to a body made by solidifying b any casting method a molten steelmade by any suit able stcelmaking method. and this includes a slab-likeingot obtained by a continuous casting method.

\Vhenever in this specification and in the appended claims reference ismade to amounts. ratios, percent ages or proportions. the weight basisis meant and in tended unless otherwise expressly stated.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. The method of producing grain-oriented siliconiron sheet whichcomprises the steps of providing a silicon-iron melt containing 2.2 to4.5 per cent silicon. manganese and sulfur in amounts in a ratio ofmanganese to sulfur less than 2.l. between about three and about 35parts per million boron. and between and 60 parts per million nitrogenin the ratio to boron of one to fifteen parts per part of boron. castingthe melt to form an ingot. hot rolling the ingot. then cold rolling tointermediate thickness. then heat treating the resulting cold-workedsheet. then cold rolling and reducing the sheet to final thickness. andfinally subjecting the cold-rolled sheet to heat treatment todecarburize it and to develop I [0)[001 secondary recrystallizationtexture in it.

2. The method ofclaim 1 in which the hot rolling step is begun with theingot at temperature in the range from 2100F to 2400F.

3. The method of claim I in which the hot rolling step is begun with theingot at temperature between 2200F and 2300F.

4. The method of claim 1 in which the sheet is reduced in thickness toabout 60 mils in the first coldrolling operation, and in which thesecond cold rolling operation results in about 80 per cent reduction inthickness of the sheet.

5. The method of claim I in which the final cold rolling step results inreduction of thickness of the siliconiron sheet of about 60 per cent.

6. The method of claim I in which the amount of manganese is from about0.0l to 0.10 per cent and the amount of sulfur is from about 0.005 to0.05 per cent.

7. The method of claim I in which the melt contains about 50 parts permillion nitrogen. about five parts per million boron are added to themelt. and in which the manganese content of the melt is about 0.035 percent and the sulfur content of the melt is about 0.030 per cent. and theingot is at 2250F at the outset of hot rolling. and the sheet thicknessis reduced to 60 mils in the first cold rolling stage and the sheet isthen normalized in hydrogen for 3 minutes at 900C and thereafter coldrolled to final thickness of about l l mils.

8. The method of claim 1 in which the manganese content of thesilicon-iron melt is at least 0.0l per cent.

9. The method of producing grain-oriented siliconiron sheet whichcomprises the steps of providing a sili con-iron melt containing 2.2 to4.5 per cent silicon. additionally containing sulfur or selenium orsulfur and selenium in amount from 0.005 to 0.05 per cent. andadditionally containing from 0.0l to 0. [0 per cent manganese in anamount in the ratio to sulfur or selenium or sulfur plus selenium ofless than 2.1. and containing between 30 and parts per million nitrogen.and finally containing incidental impurities and the balance consistingof iron. adding from about three to about 35 parts per million of boronto the melt and thereby establishing a nitrogen to boron ratio to themelt of l to l5 parts of nitrogen per part of boron. casting the melt toform an ingot hot rolling the ingot. then cold rolling to intermediatethickness. then heat treating the resulting cold-worked sheet. then coldrolling and reducing the sheet to final thickness, and finallysubjecting the cold-rolled sheet to heat treatment to decarburize it andto develop l l())[()()] secondary recrystallization texture in it.

[0. The method of claim 9 in which the metal melt contains about 0.0l9per cent selenium. about 0.004 per cent sulfur and about 0.033 per centmanganesev II. The method of claim 9 in which the metal melt containsfrom 0.0[5 to 0.037 per cent selenium. about 0.004 per cent sulfur andabout 0.03 per cent manganese.

l2. The method of producing grain-oriented SlllCUlP iron sheet whichcomprises the steps of providing a hotrollcd band containing 2.2 to 4.5per cent silicon. be tween three 35 parts per million boron. between 30and 60 parts per million nitrogen in the ratio of l to l5 parts per partof boron. and amounts of manganese and sultur in the ratio of manganeseto sulfur less than ll. cold rolling the hot-rolled band to intermediatethickness. then heating the resulting cold-worked sheet, then coldrolling and reducing the sheet to final gauge thickness. and finallysubjecting the cold-rolled sheet to heat treatment to develop( 1 l0)|001 secondary recrystallization texture in it.

[3. A silicomiron hot-rolled band containing 2.3 to 4.5 per centsilicon. manganese and sulfur in amounts in a ratio of manganese tosulfur less than 3. l between about three and 35 parts per millionboron. and between 30 and 60 parts per million nitrogen in the ratio toboron of l to l5 parts per part of boron.

1. THE METHOD OF PRODUCING GRAIN-ORIENTED SILICON-IRON SHEET WHICHCOMPRISES THE STEPS OF PROVIDING A SILICON-IRON MELT CONTAINING 2.2 TO4.5 PER CENT SILICON, MANGANESE AND SULFUR IN AMOUNTS IN A RATIO OFMANGANESE TO SULFUR LESS THAN 2.1, BETWEEN ABOUT THREE AND ABOUT 35PARTS PER MILLION BORON, AND BETWEEN 30 AND 60 PARTS PER MILLIONNITROGEN IN THE RATIO TO BORON OF ONE TO FIFTEEN PARTS OF BORON, CASTINGTHE MELT TO FORM AN INGOT, HOT ROLLING THE INGOT, THEN COLD ROOLING TOINTERMEDIATE THICKNESS, THEN HEAT TREATING THE RESULTING COLD-WORKSHEET, THEN COLD ROLLING AND REDUCING THE SHEET TO FINAL THICKNESS, ANDFINALLY SUBJECTING THE COLD-ROLLED SHEET TO HEAT TREATMENT TODECARBURIZE IT AND TO DEVELOP (110)(001) SECONDARY RECYSTALLIZATIONTEXTURE IN IT.
 2. The method of claim 1 in which the hot rolling step isbegun with the ingot at temperature in the range from 2100*F to 2400*F.3. The method of claim 1 in which thE hot rolling step is begun with theingot at temperature between 2200*F and 2300*F.
 4. The method of claim 1in which the sheet is reduced in thickness to about 60 mils in the firstcold-rolling operation, and in which the second cold rolling operationresults in about 80 per cent reduction in thickness of the sheet.
 5. Themethod of claim 1 in which the final cold-rolling step results inreduction of thickness of the silicon-iron sheet of about 60 per cent.6. The method of claim 1 in which the amount of manganese is from about0.01 to 0.10 per cent and the amount of sulfur is from about 0.005 to0.05 per cent.
 7. The method of claim 1 in which the melt contains about50 parts per million nitrogen, about five parts per million boron areadded to the melt, and in which the manganese content of the melt isabout 0.035 per cent and the sulfur content of the melt is about 0.030per cent, and the ingot is at 2250*F at the outset of hot rolling, andthe sheet thickness is reduced to 60 mils in the first cold rollingstage and the sheet is then normalized in hydrogen for 3 minutes at900*C and thereafter cold rolled to final thickness of about 11 mils. 8.The method of claim 1 in which the manganese content of the silicon-ironmelt is at least 0.01 per cent.
 9. The method of producinggrain-oriented silicon-iron sheet which comprises the steps of providinga silicon-iron melt containing 2.2 to 4.5 per cent silicon, additionallycontaining sulfur or selenium or sulfur and selenium in amount from0.005 to 0.05 per cent, and additionally containing from 0.01 to 0.10per cent manganese in an amount in the ratio to sulfur or selenium orsulfur plus selenium of less than 2.1, and containing between 30 and 60parts per million nitrogen, and finally containing incidental impuritiesand the balance consisting of iron, adding from about three to about 35parts per million of boron to the melt and thereby establishing anitrogen to boron ratio to the melt of 1 to 15 parts of nitrogen perpart of boron, casting the melt to form an ingot, hot rolling the ingot,then cold rolling to intermediate thickness, then heat treating theresulting cold-worked sheet, then cold rolling and reducing the sheet tofinal thickness, and finally subjecting the cold-rolled sheet to heattreatment to decarburize it and to develop (110)(001) secondaryrecrystallization texture in it.
 10. The method of claim 9 in which themetal melt contains about 0.019 per cent selenium, about 0.004 per centsulfur and about 0.033 per cent manganese.
 11. The method of claim 9 inwhich the metal melt contains from 0.015 to 0.037 per cent selenium,about 0.004 per cent sulfur and about 0.03 per cent manganese.
 12. Themethod of producing grain-oriented silicon-iron sheet which comprisesthe steps of providing a hot-rolled band containing 2.2 to 4.5 per centsilicon, between three 35 parts per million boron, between 30 and 60parts per million nitrogen in the ratio of 1 to 15 parts per part ofboron, and amounts of manganese and sulfur in the ratio of manganese tosulfur less than 2.1, cold rolling the hot-rolled band to intermediatethickness, then heating the resulting cold-worked sheet, then coldrolling and reducing the sheet to final gauge thickness, and finallysubjecting the cold-rolled sheet to heat treatment to develop (110)(001)secondary recrystallization texture in it.
 13. A silicon-iron hot-rolledband containing 2.2 to 4.5 per cent silicon, manganese and sulfur inamounts in a ratio of manganese to sulfur less than 2.1, between aboutthree and 35 parts per million boron, and between 30 and 60 parts permillion nitrogen in the ratio to borOn of 1 to 15 parts per part ofboron.